Using multi-criteria decision analysis to assess the vulnerability of drinking water utilities

Outbreaks of microbiological waterborne disease have increased governmental concern regarding the importance of drinking water safety. Considering the multi-barrier approach to safe drinking water may improve management decisions to reduce contamination risks. However, the application of this approach must consider numerous and diverse kinds of information simultaneously. This makes it difficult for authorities to apply the approach to decision making. For this reason, multi-criteria decision analysis can be helpful in applying the multi-barrier approach to vulnerability assessment. The goal of this study is to propose an approach based on a multi-criteria analysis method in order to rank drinking water systems (DWUs) based on their vulnerability to microbiological contamination. This approach is illustrated with an application carried out on 28 DWUs supplied by groundwater in the Province of Québec, Canada. The multi-criteria analysis method chosen is measuring attractiveness by a categorical based evaluation technique methodology allowing the assessment of a microbiological vulnerability indicator (MVI) for each DWU. Results are presented on a scale ranking DWUs from less vulnerable to most vulnerable to contamination. MVI results are tested using a sensitivity analysis on barrier weights and they are also compared with historical data on contamination at the utilities. The investigation demonstrates that MVI provides a good representation of the vulnerability of DWUs to microbiological contamination.     

Process performance and polyphosphate-accumulating organism-glycogen-accumulating organism communities in an anaerobic/anoxic/oxic system operated with different carbon sources

A pilot plant anaerobic/anoxic/oxic (A2/O) system fed with domestic wastewater was operated to examine the effect of varying different types of carbon source (acetic acid, propionic acid, and glucose), added as a complement to the wastewater, on the (1) process performance and (2) microbial population. The operational condition that lead to a significant removal of total nitrogen (82%) was achieved with acetic acid. When the complementary carbon source was propionic acid, an improved removal efficiency of orthophosphate (97%) was observed. Because this finding was concurrent with higher polyphosphate-accumulating organism (PAO) population fractions detected using fluorescent in situ hybridization analysis (41.9 +/- 3.0%), it suggests that members of PAO populations that were able to reduce nitrate gained importance over PAO members that could not, thus improving the denitrifying phosphorus removal.     

Feasibility assessment of electrocoagulation towards a new sustainable wastewater treatment

BACKGROUND, AIM AND SCOPE: Electrocoagulation (EC) may be a potential answer to environmental problems dealing with water reuse and rational waste management. The aim of this research was to assess the feasibility of EC-process for industrial contaminated effluents from copper production, taking into consideration technical and economical factors. EC-technology claims to offer efficient removal rates for most types of wastewater impurities at low power consumption and without adding any precipitating agents. MATERIALS AND METHODS: Real wastewater from Saraka stream with high concentrations of heavy metals was provided by RTB-BOR, a Serbian copper mining and smelting complex. Runs were performed on a 10 l EC-reactor using aluminum plates as sacrificial electrodes and powered by a 40 A supply unit. Results concerning key factors like pH, conductivity and power consumption were measured in real time. Analysis of dissolved metal concentrations before and after treatment were carried out via ICP-OES and confirmed by an independent test via AAS. RESULTS: Several aspects were taken into account, including current density, conductivity, interfacial resistivity and reactor settings throughout the runs, in order to analyze all possible factors playing a role in neutralization and metal removal in real industrial wastewater. DISCUSSION: Electrode configurations and their effects on energy demand were discussed and exemplified based on fundamentals of colloidal and physical chemistry. CONCLUSIONS: Based on experimental data and since no precipitating agents were applied, the EC-process proved to be not only feasible and environmentally-friendly, but also a cost-effective technology RECOMMENDATIONS AND PERSPECTIVES: The EC-technology provides strategic guidelines for further research and development of sustainable water management processes. However, additional test series concerning continuous operation must be still performed in order to get this concept ready for future large-scale applications.     

Strength and workability of masonry mortars manufactured with ladle furnace slag

Ladle furnace basic slag (LFS) is a by-product of the steelmaking process. It has rarely been recovered in the past and is usually disposed of in landfill sites. Despite containing stable chemical substances of great quality, some of which are potentially hydraulic, its practical applications have been limited. This paper discusses the attractive option of using LFS in the manufacture of masonry mortars for use in the construction industry, which requires an analysis of the principal characteristics of such mortars, i.e. workability and mechanical strength. It reports on a comparative study, using standard commercial admixtures, between conventional masonry mortars and mortars manufactured with LFS as a partial replacement for sand and cement, the results of which imply considerable economic savings in sand and cement, improvements in the properties of the mortars and in overall sustainability, by avoiding disposal and conserving natural resources.     

Aerosols in a Mediterranean Forest: Sulfates,Particle Size Distribution,and Growth Rates

ABSTRACT

Particle size distribution measurements in 16 nonlinear intervals covering the 0.1–7.5 μm range and concurrent sulfate concentrations were continuously recorded in September 1996 over the period of two weeks in a Mediterranean forest. Sulfate size distribution was derived from a linear correlation fit between the concentrations and the number of particles recorded at each particle size interval. The results revealed two modal diameters for sulfates, with typical diameters at 0.3 and 0.675 μm. These results were associated with two different dominant chemical mechanisms governing sulfate formation.

In order to describe the dominant chemical mechanism, the growth law approach was applied. Growth rates were determined using the parameter estimates of the fitted particle size distribution function. By matching these data with sulfate concentrations, the dominant chemical reactions were identified. The results have shown that sulfate formation is governed by both homogeneous and heterogeneous reactions and that the latter process was dominant. Condensation reactions prevailed in the early morning and late afternoon, and volume reactions at night, particularly in high-moisture conditions. From the observational data, the gas-to-particle conversion rate for sulfur dioxide (SO₂) at nighttime was also derived, yielding a 2.18%/hr^-1.     

Long-Term Efficiency of Catalytic Converters Operating in Mexico City

ABSTRACT

A 1999 ordinance by the Government of Mexico City bans 1993 model-year vehicles from on-road operation if their catalytic converters are not replaced with new ones. To validate the benefits of this action, we examined three issues related to exhaust emissions of vehicles equipped with catalytic converters. After selecting representative fleets of in-use vehicles, a comparison between emissions and catalyst efficiency in cars with two categories of exhaust emission limits was carried out. For that purpose, two fleets were selected, each made up of 10 vehicles run under similar conditions. A third, larger fleet with emissions control systems was used to evaluate and simulate real-world conditions of vehicles in a controlled laboratory. Finally, the aging effect on the catalytic converter was studied on vehicles run for 100,000 km, replacing their old emission control devices for new ones.

The 1991-1992 model-year vehicles showed a high percentage of compliance with the corresponding emissions standard (90%) in comparison with 1993 model-year and later vehicles (Tier 0). However, NO_x emissions were higher for the newer vehicles. Fifty percent of the 1991-1992 model-year vehicles evaluated under the official inspection/maintenance (I/M) procedure did not meet the regulated emissions standard when the results were compared with those of the U.S. Federal Test Procedure     

Evaluation of a multiresidue method for pesticides in cereals using supercritical fluid extraction and gas chromatographic detection

Supercritical fluid extraction (SFE) was evaluated to be applied for residue analysis of 22 gas chromatography/electron capture detector-nitrogen phosphorus detector (GC/ECD-NPD) amenable pesticides in rice, wild rice and wheat. Samples were extracted with supercritical carbon dioxide at 200 atm pressure and 50°C temperature, using methanol as a static modifier. Mean recoveries obtained with the proposed SFE method at two spiking levels with four replicates per level are compared with those obtained with an ethyl acetate-based solvent extraction/gel permeation chromatography (GPC) clean up method. Both methods gave consistent high recoveries for almost all the pesticides from all the commodities with overall mean recoveries higher than 70% with relative standard deviations lower than 20%. Remarkable exceptions were captafol and dimethoate, for which low and/or non-reproducible recoveries were obtained with the SFE method. Residue levels determined with both methods in nine different incurred samples of wheat, containing some of the studied pesticides, were very similar, but, in all cases, slightly higher levels were determined with the SFE method.     

The transboundariness approach and prioritization of transboundary aquifers between Mexico and Texas

“Transboundariness” refers to a new approach that identifies and prioritizes transboundary aquifers using socio-economic and political criteria, improving their characterization by using other variables in addition to their mere physical boundaries. This approach is applied to the hydrogeological units/aquifers shared by Mexico and Texas, with the following results. First, the rankings agree with the current level of attention to transboundary aquifers in the region by both countries, providing a quantifiable system that could be tested in other transboundary aquifers. Second, this approach provides a holistic and integrative perspective for transboundary aquifer assessment and prioritization. Third, this prioritization exercise expands the criteria currently used into a more integrative regime of groundwater links to the community as a whole. Finally, the results reflect not only how the transboundary aquifers are being used (or neglected) but also the socio-political context of the populations that depend on these resources for current and future development.     

Genealogical Analysis of a Closed Herd of Black Hairless Iberian Pigs

Abstract: Livestock breeds are recognized as important components of world biodiversity. The Iberian pig is a swine breed well adapted to the Mediterranean forest ecosystem and provides cured products of high quality. The ancient population of Iberian pigs (  Sus scrofa meridionalis ) was differentiated in several local types, the black hairless pigs representing the fattest genetic type. The conservation program of the Guadyerbas strain has maintained this germplasm isolated since 1945 as a closed population in an experimental herd. The complete pedigree, with 1000 breeding animals descending from 24 founders, has been used to measure along the successive cohorts of breeding animals the effective number of founders, effective number of nonfounders, founder genome equivalents, and expected number of founders' surviving alleles. For the last cohort, the values were 10.34, 1.42, 1.25, and 4.06, respectively. The evolution of inbreeding and coancestry and its components attributable to each founder were also studied. The rate of increase in inbreeding and coancestry was 2.21% per cohort, or 0.906% per year. Finally, the effect of family structure and mating tactics on the evolution of coancestry was also analyzed. The greatest rates of coancestry per cohort were attributable to unbalanced family sizes, and the use of minimum coancestry matings effectively delayed the increase in inbreeding.     

Effectiveness of three configurations of membrane bioreactors on the removal of priority and emergent organic compounds from wastewater: comparison with conventional wastewater treatments

In this work the effectiveness of membrane bioreactors as advanced treatment on the removal of emergent and priority organic compounds in wastewater treatment plants has been evaluated during a one-year monitoring study. The studied wastewater treatment plant operates with flat sheet and hollow fibre membranes in two parallel lines. Moreover, a reverse osmosis module connected in series after the hollow fibre membrane was evaluated for one month. Comparison of membrane bioreactor and conventional activated sludge treatment was also investigated, as well as the influence of the physicochemical properties of the compounds on the removal rates achieved. Sixteen pharmaceutical compounds belonging to seven therapeutic groups and eight priority organic pollutants, including linear alkylbenzene sulfonates, nonylphenol and its ethoxylates and phthalate, were monitored. The highest mean concentrations corresponded to priority organic pollutants (309 μg L(-1) of linear alkylbenzene sulfonate C(12)) followed by pharmaceutical compounds (24.5 μg L(-1) of ibuprofen). No significant difference of effectiveness was found among flat sheet and hollow fibre membranes. However, an improvement was obtained with the addition of a reverse osmosis module for most of the compounds. Biodegradation has been shown as the main route involved in the removal of organic compounds during both technologies.